Sugar production from lignocellulosic biomass is a key contributor to overall costs in the biomass-to-ethanol process, and enzymatic hydrolysis of cellulose offers advantages over other chemical conversion routes such as a mild operation environment, higher yields and minimal byproducts generation. Batch enzymatic hydrolysis with high solids loadings has been challenged by obstacles such as the elevation of reaction viscosity and inhibition by lignin, either through nonproductive binding or physical interference. Fed-batch approach has been studied and a potential advantage is the maintenance of a lower solids loading during the course of the hydrolysis reaction. Fed-batch operations enable superior control as they provide different avenues for process control through distinct phases of substrate digestion and enzyme consumption. By programming substrate feeding, one can control important phenomena such as solids content and end-product inhibition. Hence, the performance of fed-batch hydrolysis highly depends on timing and amount of substrate feeding operations.
The system described herein provides a method to optimize these control opportunities and still meet the desired objectives.